The invention relates generally to process control. More specifically, the invention relates to interfacing a demand response system with a Programmable Logic Controller (PLC).
Residential and commercial buildings consume more than 70% of all electricity generated. Therefore, electricity consumption in buildings plays a major role in smart grid. Next to energy efficiency and renewable power generation, peak load reduction is an important goal for smart grid.
Demand Response (DR) is a way to change the electric usage by end-use customers from their normal consumption patterns in response to DR signals. The benefits are that by shedding electricity consumption during peak use hours the need for peaking power plants is reduced. Another benefit is the overall electricity consumption will be reduced when supply is short (e.g., renewable energy generation fluctuation, major equipment failure in the power grid, etc.).
DR manages customer consumption of electricity in response to supply conditions. DR mechanisms respond to explicit requests to shed load. DR involves curtailing power used or by starting on site generation which may or may not be connected in parallel with the grid. DR is a component of smart energy demand, which includes energy efficiency, home and building energy management, distributed renewable resources, and electric vehicle charging.
Current DR schemes are implemented through the use of dedicated control systems to shed loads in response to a request by a utility or market price conditions. Services (lights, machines, air conditioning) are reduced according to a preplanned load prioritization scheme during the critical time frames. An alternative to load shedding is on-site generation of electricity to supplement the power grid.
DR is typically used to reduce demand. Depending on the configuration of generation capacity, DR response may also be used to increase demand (load) at times of high production and low demand.
There are two types of DR—emergency demand response and economic demand response. Emergency DR is needed to avoid power outages. Economic DR is used to assist utilities manage daily system peaks.
Today's Networked Control System (NCS) is a Distributed Control System (DCS) whose components (process sensors, controllers, process actuators, etc.) are distributed using digital network technology. An NCS is a control system where control loops are closed through a real-time DCS. Process signals (process variables) from transmitters, sensors, etc., and control signals (control variables) to actuators, valves, etc., are exchanged among the components as information packages through a network.
What is needed is a method and system that provides an operational interface between a facility control system and a DR system.